Timing Animal Reproductive Cycles

Using Hormones to Help Breeding

Every species has its own unique reproductive cycle, dependent on biology and environment. Some animals are seasonal breeders; others can mate year round. Some species require specific foods, light cycles or behavioral prompts to mate, and estrous time, gestational period and duration between births can all vary.

Zoos are very careful to make the right matches to ensure the long-term health of the populations in their care. But how to know if animals are fertile, mature, receptive or ready for breeding?

Hormones can help. By measuring testosterone, estrogen and progesterone over time—the same hormones that guide reproduction in humans—endocrinologists can gain insight into animal reproductive cycles. This can provide valuable insight for ensuring baseline health and choosing the right time to introduce potential partners.

Most reproductive hormone measurements, at the zoo and in the wild, come from non-invasive fecal samples. Reproductive research projects can harness an abundant resource without bothering the animals, gathering valuable information to improve conservation and care.